This invention relates to a device that automatically vents gas, for example air, from a liquid filled system, for example water.
Temperature change liberates gas present in solution which is precipitated in closed systems such as radiators causing reduced system efficiency. Gas venting devices are used in industrial and domestic applications as a means to expel gas products from liquid-filled systems so as to maintain the system efficiency. The most common example is an air vent valve on top of a domestic hot water radiator which is manually operated periodically by a key to release air that has entered the system.
Automatic vents are available and tend to fall into two categories (or a combination thereof). The first type currently commercially available is a float on a lever type vent which utilises raising water levels in the system to elevate a float which exerts force via a lever on a valve to close the air way. The weight of the float and lever cause the valve to open when the water level drops so allowing expulsion of unwanted air. This type is reliable, but large, due to the necessary weight of the float to open the airway against a pressure difference between system pressure inside the radiator and that of atmospheric pressure outside. This makes it aesthetically unacceptable, eliminating it as a viable option for fitting to most domestic radiators and is traditionally fitted as a single unit to a system high-point, which does not then vent air already collected in radiators.
The second type is a hygroscopic vent which is small but liable to leak water. Its operating principle utilises a series of fibre washers that allows the passage of air when they are dry but expand when contacted by water thus closing an exit port. This has been considered unreliable and British Standard BS 5449 does not recommend this type as it may permit water to escape for the first few seconds until the fibre washers expand.
The object of this invention is to provide an improved and more reliable automatic vent that is small, doesn't leak water, and may therefore be more acceptable for domestic and other applications that require miniaturisation of the vent.